The present invention is directed to a replaceable cartridge filter and backwash control system for filtration of drinking water. The system includes a valve for controlling the flow of filtered water and backwash discharge. Filtration of drinking water may be accomplished by employing any of several types of commercially available filters, including granular activated carbon bed filters, solid block carbon media filters and carbon media cartridge filters. Granular activated carbon bed filters and solid block carbon media filters may be rejuvenated by periodic backwashing or reverse flushing with hot water. Backwashing, when performed with water of 140.degree. F. or more, has benefits similar to pasteurization, in that, the hot water will destroy most of the bacteria present in the filter while flushing accumulated sediment and debris therefrom. Filter units incorporating these types of filters must be returned to the seller for carbon replacement after a limited number of backwashing cycles, since backwashing shortens the life of the filter. A carbon media cartridge filter may be purchased and easily replaced by the user himself. Prior to the present invention, hot water backwashing was not used with carbon media cartridge filters. Therefore, the life of the carbon media cartridge filter could not be extended. The cost of a replacement cartridge coupled with the inconvenience to the user and the complexity of changing the filter, often prompts him to ignore the recommended replacement schedule and hence, his cartridge carbon media filter becomes essentially ineffective. Numerous arrangements of various types of water filters are shown in the prior art U.S. Pat. Nos. 3,316,937, 3,707,233, 3,977,433, 4,105,555, 4,115,276, 4,301,009, 4,515,692, 4,553,566. None of these patents discloses the features of the present invention.